Overview
Naspolini et al. measured arsenic (As), lead (Pb), mercury (Hg), and cadmium (Cd) in 185 human milk samples from the Germina prospective cohort in São Paulo, Brazil, collected at 3 months postpartum, and assessed associations with infant neurodevelopment via the Bayley-III scales at 3, 5–9, and 10–16 months of age. Arsenic had the highest detection rate (38.6%, mean 2.76 µg/L), followed by Hg (23.9%, mean 1.96 µg/L) and Pb (22.8%, mean 2.09 µg/L); Cd was not detected above LOQ in any sample. Infants exposed to Pb in human milk showed significantly lower language development trajectories at 10–16 months compared to non-exposed infants (β = −0.413; 95% CI −0.653 to −0.173), even though mean Pb concentrations in this cohort were lower than in most prior Brazilian and international studies.
Key numbers
Arsenic total arsenic (tAs): n=185; detection rate 38.6% (71/185); mean (SD) 2.76 (4.09) µg/L; range 0.10–34.55 µg/L. LOQ 0.06 µg/L. Note: speciation not performed; these are total As by ICP-MS.
Mercury total mercury (tHg): n=185; detection rate 23.9% (44/185); mean (SD) 1.96 (6.68) µg/L; range 0.04–54.41 µg/L. LOQ 0.3 µg/L. Note: speciation not performed; total Hg by ICP-MS.
Lead (Pb): n=185; detection rate 22.8% (42/185); mean (SD) 2.09 (5.36) µg/L; range 0.15–40.90 µg/L. LOQ 1 µg/L. Among 42 exposed infants, mean Pb 8.67 (8.43) µg/L. At 10–16 months, exposed infants had mean language Bayley score 97.47 (13.36) vs. non-exposed 102.96 (11.53) (p<0.001).
Cadmium (Cd): n=185; 0 detections (all below LOQ of 0.08 µg/L).
Neurodevelopmental outcome: Pb exposure × infant age interaction: β = −0.413 (95% CI −0.653 to −0.173, p<0.001) in a linear mixed-effects model adjusted for infant age, socioeconomic status, maternal education, infant sex, and pseudoweights for population representativeness.
Methods
Germina cohort, São Paulo metropolitan area, 2021–2022. Analysis by ICP-MS (PerkinElmer NexION 300D) at INCOS/Fiocruz, Rio de Janeiro. Acid digestion with 65% nitric acid. LOD/LOQ: Pb 0.015/1 µg/L; Hg 0.007/0.3 µg/L; Cd 0.002/0.08 µg/L; As 0.003/0.06 µg/L. Values below LOQ imputed as LOD/2. Since imputation rate for Pb exceeded 50%, infants were classified dichotomously as exposed vs. non-exposed for statistical analysis. Neurodevelopment assessed by Bayley-III at three time points (3 months; 5–9 months; 10–16 months). Longitudinal analysis used linear mixed-effects model (nlme R package). Basis: liquid (µg/L in whole human milk).
Implications
Certification: Human milk is not a certified product category, but Pb levels in human milk reflect maternal body burden from dietary and environmental exposures. These data anchor the exposure side of the infant-food Pb risk picture: infants exposed to as little as mean 8.67 µg/L Pb in human milk show measurable language developmental deficits, setting context for why infant food Pb limits matter.
Health: Supports no-safe-level Pb exposure framework for infants; language effects observed at concentrations lower than in most prior Brazilian state studies, consistent with the CDC/WHO consensus that no threshold exists for Pb neurodevelopmental toxicity.
Courses: Demonstrates that Pb, tAs, and tHg contamination of human milk occurs in urban Brazil; Cd was below detection, providing a contrast to other matrices. Germina cohort design provides longitudinal neurodevelopmental outcome data paired with exposure measurement.
App/Microbiome: Out of direct product scope but relevant to exposure modeling for breastfed infants.
Related evidence
- Breastmilk
- Lead
- Arsenic
- health/lead-neurodevelopment
Update history
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